Not a standard linker script, not unusual for a custom micro-controller target of course. Perhaps forked a long time ago. It however can be easily reverse-engineered, GCC has always used the ELF format for object files. Google "elf section attributes", out pops this hit, pretty helpful here.

So you got alloc, exec, write, progbits. Aha, p == progbits. So (w!xp) surely should be interpreted as "section is writable, not executable, initial data is stored in the executable image".

Nothing very special, that's the traditional .data section in a C program. Compare to .bss, not p.